Differential hoist



May 6, 1947. L. FOOTE DIFFERENTIAL HOIST 1944 3 Sheets-Sheet 1 FiledSept. 2

INVENTORT LEONARD FOOTE.

AT TORNE).

May 6, 1947. L. FOOTE DIFFERENTIAL HOIST Filed Sept. 2, 1944 5Sheets-Sheet 2 INVENTORT LEONARD FOOTE.

AT TORNE K May 6, 1947. FOQTE 2,420,072

DIFFERENTIAL HOI ST Filed Sept. 2. 1944 s Sheets-Sheet s INVENTOR.

LEONARD FOOTE.

A T TO/PNE V.

Patented May 6, 1947 UNIT ED STAT ES PAT EN T OFF ICE;

$420,072- DIFFERENTIAL nols'r Leonard Foote, Palo:Alto-,- Calif.Application September 2, 19d4,SeriaLNo.l552,82

4' Claims. (01. 114- 51) The present: invention. relates to improvementsinc-differential hoist systems. and more particulanly to noveldifierentialz heist systems suitable fQIFXHSB? inmarine' salvageandana-logous operatimes,

The conventional: differential hoist, whichv is also'oommonly knownzaatherWeston differential pulley; block; has certain; inherentdisadvantages which render. it unsuitable for-many types of lift-- ing;and; other operations. One of the primary dilate hacks istheifact-thatthewestondifferentialpulleybloclqin conventional; design,cannot be practicably made and utilized in the: largesizes necessaryfonmarine; salvage and: analflgpus opcitations;

In an ohiectof thezpresent, invention to pro-- videamimproved;vdiffierentiali hoist arrangement which: may berpracticahly constructedin. any desired? size? and! in which the: mechanical energy1.983651113131161 form, oiiriction: are greatly reduced. A furtherobject. isstot providean impnove'd drivesystemifon diiierentialihoists'.Another and gri manyobject is-to,.=provide a differential: hoist;particularly adapted for use ins submarine hoisting. AvSiFi-ilfurtherobject isto; provide: a. combined} difierential hoist-and buoyancytank-a In a -pre:-- i erredvembodiment of the; inventiomit is; an ob:-jecttwprovida a: combined differentialhoist. and buoyancy tank: togetherwith. am internal drive mechanism for. the differential hoist disposedWithin the. buoyancy tank Other objects,v togather with-some oi theadvantages to be;derived in utilizing the present invention; will becomeap Qarent from. the following detailed-l description thereof, taken.together with. the; accompanying: drawings forming a: part ofthespecificatiom, and? wherein: t

Figure 1 is a sideelevation of acombineddififerentialrhoist and buoyancytank: withlinternal: driveforthezhoist.

iligurezzis an. enlarged end: elevation, partlyim section=,.throug-h;2-2: of. Figure: 1;

Figure, 3-is a1 schematic/side View of a medifledi format the inventionemploying auxiliary buoy army; means; for the'difierential hoist.

Eigure 4; an: end view of the arrangement: shown in Figure 3-,

Figure 5- is a. side elevation of. a modificatiomoi thearrangementshewnain Figure Figure 6- a schematic; plan. View of another;modification of. the: invention; employing external: drive means for.the differential] hoist whom uti-e lized for submarinehoisting.

Figure '7 is aiside-elevationiof theschematicvlew showninhigure 6.

Figure 8 is a schematic" plan view" of a modification oi the invention"illustrating the uti' lization of a combined buoyancy tank anddifferential' hoist for other than submarine hoisting;

purposes. l V I Figure Qisa side elevation of the'schematicview shown inFigure 8. 4

Referring particularly to Figures I'a'rid zfthe differential hoistingarrangement comprises 'a;

. fioating'buoyancy tank-formedioftwo rigidly connecte'd" tubularsections I and 2 section f 2} i-beirig; smaller in diameter" thansection I in a rati'o'preferablyfalling within the range commonly em,ployedin conventional differential hoists, 'i. e., the ratioof thediameter (13)" of th'e' larger section lito the diameterldf of thesmalle r'section lie within the approximate range of 11:10; to 25:24.Cable means 5 in the form of rope; chain; steel" wire or the like isattached at one end at 3 to section I of the, buoyancy tank and partofthelength thereof is spooled' on section! or the buoyancy tank; Thecable passes from section I through a single sheave pulley block 1,which support-sa load hack, 8, and is spooled' on section 2 of thebuoyancy tank, being rigidly attached thereto at 41 The buoyancy tank isrotatedjlo'y means of an internal drive mechanism generally indicated atl 0 and described indetail hereinafter; Power'conduit means 9 entersthe'buoyan'cy tank through a conventionalwater tight rotatabfet bushingat 23". I c y 7 An annular geartracl'r i4 is brovi'ded in-the inter iorof thehuoyancyta'nk. Pivot arm [2 is pivotablyniouiited on ax iar shaftI which is mountedW1'thih the buoyanc tank, 'Gear'13i's rotatahlymounted on'the'end of Pivot arm I'Z'and'engages annular gear track M.Gear I5 is alsorotawny-mounted on pivotarin 1'2 andengages'gar I32'Geaii'1fi' is driven by 'geai' l l which i's mounted the drive-shaft ofmotor 1 9 which -i's"riigid1y* mounted; oncpiuot arm; I 21 Gear 'I'B isrigidly at taehedftofgear- I55 and: turns: therewith. (tounter weighinMir-is: mounted on. and: supported. bypivot amid-z. Adenventionalasolenoidbrake 2J isfl-prm vided on: motor [.9 which. issupplied current through electrical: conduit-means at 20; connected to;ele ctrical w conduit means, athrouglrbushing 23;

The) operation of, the differential hoist meche anism is asiollows; I

With the. buoyancy tank: floating -in water,,the madl hook. 8: isattached; to the underwater, load; which itdsdesireditol raise, Currentisthensupplied; til-motor ta -pivot; arm lllhei'ng raised as gearlfiisretated: lay-means oilthegear train. and travels along annular geartrack [4. counterit is desired to hold the load at the desired raised orany intermediate level. Other suitable means may be employed for brakingpurposes, if desired, as for exam le a non-overhauling worm gear may beincluded in the gear. train or .a protuber-.

ance extending to the diameter of section I of the buoyancy tank may beprovided on the smaller section 2 of the buoyancy tank, as shown indotted line at 22 of Figure 2. If the rotation of the buoyancy tank isstopped in a position whereat the cable leaving section 2 of thebuoyancy tank is adjacent protuberance 22, both sections of the buoyancytank have the same effective diameters and the differential hoist willnot overhaul itself. a

Forpurnoses of illustration, a suitable differential hoist such as shownin F res 1 and 2 ca ab e of lifting approximately 800 tons under its ownbuoyancy. is formed as a buoyancv tank 100 feet long with la er sectionI thereof feet in diameter and smaller section 2 there f 19 feet indiameter. counterwe ght I8 is positioned on pivot arm l2 a distance of 5feet from the pivoted end thereof and Wei hs 40 tons. Each rotation ofthe buoyancv tank. which serves also as the puilev drum, rai es sheave Ia distance eoual to 1r/2 feet, s nce the gener l eoua ion fordifferential hoists provides thatthe lower sheave is raised a distanceof wr(D-d) /2 with each revolutinn of the p ley drum and in the exampledescribed above D-d is edual to 1. It wil be appreciated. of course.that'the arran ement shown in Figures 1 and 2 may be ofany desired sizebest suited for the particular a plication for which it is to be emploed, small hand o erated units being s i able for raising and loweringunderwater cables, pi elines and the like and larger units beinernnloved for ship or other heavy salvage work. Furthermore, a pluralityof units of any desired size may be employed for heavy salvageoperations and the like.

In Fi ures 3 and 4 an arrangement is shown for increasing the loadcarrying-ca acity of differential hoist units of the eneral type shownin Figures 1 and 2. In this embodiment of the inyention the buoyancytank comprisingsections l and 2 is in Figure 1 is further provided withextensions 24 and 25 at o posite ends thereof. Continuous cables as at26 and 21 pass around extensions 24 and 25 respectively and throughsheaves 28 and 29 respectively. Support elements as at 3| and 33 areattached to bitts 30 and 32 respectively which are mounted on a barge 34and support sheaves 28 and 29 respectively, In this manner the loadcarried by the hoist arrangement may be greater than that which couldnormally be supported by the buoyancy tank, since the additionalbuoyancy of the barge is effectively employed. In the' arrangeinentshown, the buoyancy tank is free to rotate by means of the continuouscable supports passin lthrough sheaves 28 and 29 which are supported bythe barge. An internal drive mechanism such as shown in Figure 2 may beemployed to rotate the buoyancy tank,

In Figure 5, the differential hoist is shown mounted on bearings 3! and39 by means of shaft 35, supports 35 and 38 being provided for bearings31 and 39 respectively. In this embodiment of the invention, which issuitable for general use in other than marine applications, cable 5passes around sections I and 2 ofthe pulley drum a suflicient number ofturns to insure frictional grip thereof and the extra cable depends in ahanging loop 40, thus forming a continuous cable. The internal drivemechanism of Figure 2 is employed at 10. This arrangement is suitablefor either hand operation by means of hanging loop 40 when handlinglight loads or alternatively may be driven by the internal mechanism atII).

In Figures 6 and 7 the motive power for operating the differential hoistaccording to the present invention is provided by a tug boat 48. The

diilerential hoist comprises a double unit consisting of two smallersections at 43 and 44 and two larger sections 42 and 45, the foursections being formed as a rigid buoyant unit. The cable 49 is attachedat one end to storage drum 41, passes around pulley drum section 43 withsumcient turns to insure frictional grip, thence through a 2-sheaveblock 53 and around pulley drum section 42 with sufficient turns toinsure frictional grip. From pulley drum section 42 the cable passesthrough an equalizing sheave 5| which is secured to bitt 52 on tug boat48, around pulley drum section with suiiicient turns to insurefrictional grip, through 2-sheave block 53, around pulley drum section44 with sufficient turns to insure frictional grip and terminatesonstorage drum 46. The cables leading from the storage drums 45 and 41 topulley drum sections 43 and 44 are normally maintained in a slackcondition. Load hook 54 is carried by 2-sheave block 53 and is attachedto a hulk 55 or other load which it is desired to lift. As tugboat 43moves away from the differential hoist under its own power, the loadexerted on the cable leading from equalizing sheave 5| to pulley drumsections 42 and 45 causes the pulley drum unit to rotate and thus raisethe load, while at the same time cable is continuously fed to pulleydrum sections 43 and 44 from storage drums 4E and 41. The

double differential hoist unit in combination with the equalizing sheavemounted on the tug boat prevents twisting of the hoist unit as the loadis placed on the driving cables.

Figures 8 and 9 illustrate the utilization of the present differentialhoist unit for refioating beached vessels and analogous operations. Thebuoyancy tank 55 is provided with a section of reduced diameter at 51.Cable 58 is secured to a bitt 60 on a towing vessel 65, passes aroundthe buoyancy tank 55 with sufficient turns to insure frictional grip,through a sheave 59, around section 5'! of buoyancy tank 56withsuflicientturns to insure frictional grip and terminates on storagedrum 6| mounted on towing vessel 55. A pair of anchors 54, 53 aredisposed seawardly from buoyancy tank 55 and secure buoyancy tank 56against shoreward movement by means of cable 62 which leads from anchor63 through buoyancy tank 56 to anchor 64. Alternatively, separate cablesmaybe employed toeach anchor with swivel attachments to buoyancy tank53, the essential requirement being that the buoyancy tank is free torotate with respect to the anchor cables. Load hook 60 is attached tothe beached vessel and the hoist operated by towing'vessel which, inmoving seawardly, applies a load to the cable leading from bitt 60 tobuoyancy tank 56 which brings about the rotation of the buoyancy tankand consequently exerts a pulling or O sheave 59 and load hook 60. Cableis continuously supplied to section 51 of buoyancy tank 56 from storagedrum 60, the line from the storage drum normally being maintained slack.Anchors 64 and 63 prevent both the tendency of the buoyancy tank totwist and to move shoreward as the load is exerted by towing Vessel 65.

Various advantages have been demonstrated to accrue in the utilizationof the present invention, as for example the combination difierentialhoist and buoyancy tank detailed above is virtuallyv frictionless,excepting of course the friction in the lower load carrying sheave andthe bending of the cable. This is attributed to the fact that the wateris the bearing surface for the difierential pulley drum. It has beendemonstrated in practice that with an arrangement similar to thatillustrated in Figures 1 and 2, the hoist will overhaul itself with avery light load on the load hook. Further, when utilized in submarinesalvage operations, the present arrangements provide convenient meansfor storing the great lengths of cable necessary and at the same timegreatly facilitate the actual hoisting operations since it is notnecessary to sink a number of buoyancy tanks alongside the sunkenvessel, secure them to the vessel (a dangerous and time consumingoperation) and then displace the water in the tanks with air, whichnecessitates large compressor capacity and numerous air lines to thesubmerged tanks. To the contrary, employing the differential hoist ofthe instant invention, it is only necessary to secure the load carryingcables to the vessel and then operate the hoist. A further advantagelies in the constant control which is easily maintained over thehoisting operation, the load being raised as slowly or rapidly asdesired and the hoisting operation being stopped and started asconvenience dictates, as opposed to the use of submerged buoyancy tankswhich tend to bob rapidly to the surface with the load as soon as apositive buoyancy is attained by displacement of the water and whichoften results in serious and often irreparable damage.

The internal drive mechanism provides a convenient, efficient and easilycontrolled means for operating the differential hoist whether employedin combination with a buoyancy tank or mounted on bearings as shown inFigure 5.

I claim:

1. In a difierential hoist, the combination comprising a rotatablymounted differential pulley drum, including sections of larger andsmaller diameters, cable means leading from said differential pulleydrum to and supporting load carrying means to form a differential hoist,driving means arranged and adapted to rotate said differential pulleydrum internally mounted within said differential pulley drum and brakingmeans for said differential hoist comprising a protuberance on saidsmaller diameter section of said pulley drum extending to the diameterof said larger diameter section of said pulley drum.

2. In a differential hoist the combination comprising a differentialpulley drum including sections of larger and smaller diameters andformed as a buoyancy tank, cable means leading from said differentialpulley drum to load carrying means to form a differential hoist, aninternally mounted annular gear track disposed within said differentialpulley drum in a plane other than parallel to the longitudinal axis ofsaid differential pulley drum, a pivot arm pivotally mounted within saiddifferential pulley drum, a gear rotatably mounted on said pivot arm andengaging said gear track, a counterweight supported by said pivot arm,power means mounted on said pivot arm and driving said gear mounted onsaid pivot arm through a gear train and braking means for saiddiiferential hoist comprising a protuberance on said smaller diametersection of said pulley drum extending to the diameter of said largerdiameter section of said pulley drum.

3. In a differential hoist system the combination comprising a doubledifierential pulley drum including sections of larger diameter separatedby adjacent sections of smaller diameter, said pulley drum being formedas a buoyancy tank, cable means leading from a tension equalizingelement and around said larger diameter pulley drum sections infrictional engagement therewith, said cable means thence leading througha twosheave depending load carrying element, thence around said smallerdiameter sections of said pulley drum and terminating on cable storageelements, thereby forming a double differential hoist and means forexerting a load on said tension equalizing element in a direction awayfrom said pulley drum sufiicient to rotate said pulley drum.

4. In a difi'erential hoist system, the combination comprising adifierential pulley drum including sections of larger and smallerdiameter and formed as a buoyancy tank, cable means leading from atensioning element around said larger diameter section of said pulleydrum in frictional engagement therewith, thence through load carryingsheave means, thence around said smaller diameter section of said pulleydrum in frictional engagement therewith and terminating on cable storagemeans, thereby forming a differential hoist, anchor means securing saiddifferential pulley drum against change in alignment along thelongitudinal axis thereof under load conditions and means for exertingsuflicient tension load on said tensioning element to rotate said pulleydrum.

LEONARD FOOTE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,201,337 ONeal Oct. 1'7, 19162,039,870 Adams May 5, 1936 1,104,964 Cobb July 28, 1914 475.172 Aireyet al May 17, 1892 853,238 Groash May 14, 1907 1,288,108 Messer Dec. 17,1918 1,264,257 Beckwith Apr. 30, 1918 1,268,082 Beckwith June 4, 1918FOREIGN PATENTS Number Country Date 13,249 Great Britain 1913

